Instant noodles can be divided into two types: fried noodles prepared by frying and drying noodles; and non-fried noodles prepared by drying noodles without frying. Non-fried noodles have noodle strings giving a denser feeling than that of fried noodles, and provide a texture closer to that of fresh noodles, but sticking of the noodle strings is liable to occur at the time of drying so that the noodle strings may become hard to loosen. There are several methods for drying non-fried noodles. The general one is a hot-air drying method in which noodles are dried for about 30 to 60 minutes by being exposed to the hot air having a wind speed of around 5 m/s or less and a temperature of around 70 to 100° C. Additional examples of the method include a low-temperature drying method in which noodles are dried for a long time at a low temperature, and a high-temperature and high-speed flash drying method in which noodle strings are exposed to a high-temperature and high-speed air flow at around 100° C. to 200° C. as disclosed in Patent Document 1.
Typically, in the case of fried noodles, the noodles acquire a fixed shape while floating in frying oil with moisture evaporation, and therefore a mass of the noodles is relatively bulky and the sticking of the noodle strings is relatively less likely to occur. In the case of non-fried noodles, however, since gelatinized noodles are put into a retainer and dried in the air, the noodle strings are compressed downward by the force of gravity so that the noodle strings are easily in contact with each other, and particularly in the lower surface of the noodle mass, the noodle strings collect in a high concentration, resulting in easy sticking thereof. When the sticking of noodle strings occurs, the noodle strings are hard to loosen at the time of cooking or eating, and hot water is less likely to penetrate in the stuck noodle strings at the time of cooking. The part in which hot water does not sufficiently penetrate fails to be rehydrated, and thus is deteriorated in texture.
As a technique for preventing the sticking of noodle strings, for example, there is known a method in which noodle strings are loosened by blowing air onto a noodle mass in a retainer as disclosed in Patent Documents 2 and 3. However, the loosening devices disclosed in Patent Documents 2 and 3 are intended to improve the loosening of noodle strings in such a manner that the noodle strings put in the retainer are separated so as not to form a mountain-like mass in the retainer, failing to provide a sufficient loosening effect. Particularly, in these devices, the noodle strings are pushed toward the bottom of the retainer, especially toward a corner portion (peripheral portion) of the bottom of the retainer, so that sticking of noodle strings in such a position may occur.
On the other hand, for the purpose of reducing the sticking of noodle strings and improving the loosening thereof, there is an option of preparing a bulky-shaped noodle mass to reduce the contact area among the noodle strings as much as possible. Such a technique for drying noodles while preventing the sticking of noodle strings by preparing a bulky noodle mass is disclosed in Patent Documents 4 and 5.
The invention in Patent Document 4 defines the density of a mass of non-fried noodles that are easily loosened with good rehydration (restorability). The document discloses, as a method for preparing the noodle mass with a low noodle mass density, a method in which wind having a low temperature (30° C.) is blown upward from below the noodle mass at a wind speed of 5 m/s.
Patent Document 5 describes that instant noodles which are easily loosened with good restorability are provided by a technique of adjusting the water content of steamed noodles in the retainer to a predetermined level and then drying the noodles by the compressed air blown from below the retainer to prepare a bulky noodle mass. Patent Document 6 includes no direct description about sticking of noodle strings, but describes a technique of blowing the dry air from below a retainer having multiple air holes in its bottom surface to generate an air flow along the inner wall and bottom surface of the retainer so as to give buoyancy to noodle strings, and thereby drying them while preventing the noodle mass from adhering on the retainer.
All the techniques in Patent Documents 4, 5 and 6 are, however, those of blowing the air upward from below a retainer, in which the air blown from below first collides against the bottom surface of the retainer so that the force of the air is weakened, and accordingly the drying efficiency is reduced and the effect of improving the loosening of noodle strings may not be sufficiently attained.